Electric-arc lamp.



J. THULIN. ELEGTRIG ARO LAMP.

PPLIUATION FILED MAY 1, 1905.

* Patented Apr. 29, 1913.

I UNITED sTATEs PATENT oEEIcE.

JOHN THULIN, OF CHICAGO, ILLINOIS, ASSIGNOR, BY DIRECT AND MESNE ASSIGN-MENTS, OF ONE-FOURTH TO LOUIS A. FERGUSON AND ONE-FOURTH TO PETER J.SMITH, OF CHICAGO, ILLINOIS, AND ONE-FOURTH TO CLARA FAY EASTMAN, OF

ELECTRIC-ARC LAMP.

Specification of Letters Patent.

Patented Apr 29, 1913.

' means by which the amount of air wit-hin be conveniently the bulb maybe properly proportioned in keeping with the diiferent current strengthsemployed to maintain the carbon consumpi tion at a minimum.

The invention consists in the features of construct-ion, combination andarrangement of parts hereinafter set forth, illust-rated in theaccompanying drawings and more particularly pointed out in the appendedclaims.

It is customary practice to provide an arcinclosing globe or bulbwit-hin which the ends of the carbon electrodes extend to cut down theamount of air present, the gas` in the bulb being largely carbon monoxidand carbon dioxid.' In such a construction, the carbon consumption ismaterially less than if the arc were exposed directly to the air. Thevent passage leading from the interior of the bulb is usually elongatedor tortuous so that the expansion and contraction of the gas therein,due to the putiing of the arc, will not draw outside air into the bulb.But some oxygen is necessary and indeed, sufficient air must be presentto prevent the deposition of carbon on the negative electrode in amushroom formation. This necessary air in lamps now commonly in usefinds access to the bulb at. the opening in the end plate or cap throughwhich the movable electrode extends, which is not and cannot made tight.With such constructions, the admission of air cannot be satisfactorilyregulated, but in order to keep the carbon consumption at the desiredlow minimum, the amount of -'air should be regulated in keeping with theamount of the current and the size of the carbons employed.

In accordance with the (present invention,

may be accurately regulated to suit different conditions. The bestresults have been attained by making the opening through which themovable carbon passes as nearly air tight as possible and by providing avent passage of such len h and size that a proper interchange o gaswithin the bulb and air from Without is effected therethrough. I havediscovered that the minimum amo-unt of air required for the properburning of the lamp varies with the amount of current used and thesizeof the carbons employed, so that, in order to keep the carbonconsumption at the desired low minimum, it. is necessary to regulate theamount of air in accordance with the variations of current anddifferences in size of thecarbon employed. I have further discoveredthat the amount. of air admitted througha vent passage arranged for theinterchange of air and gas therethrough cannot be satisfactorilyregulated by means of a valve or like device, but a satisfactoryregulation may be etfected by properly proportioning the length anddiameter of the vent passage or tube 1n accordance with the amount ofcurrent and size of the carbon. In other words, the invention isdesigned to provide a tube or passage of considerable length, but ofsufficient cross section to permit the proper interchange of air and gastherethrough-the size and lengt-h of said tube being proportioned inaccordance with the amount of current and the size of the carbonemployed, to admit the desired minimum amount of air. Means are alsopreferably provided to vary the effective length of the passage so thatthe lamp may be employed with different amounts of current.

In the drawings, Figure 1 is a vertical section of the lower portion ofan arc lamp with the preferred form of the invention applied thereto.Figs. 2 and 3 are cross sections on lines 2 2 and 3 -3 respectively ofFig. l.

Any suitable form of arc lamp may be employed and the arc-inclosing bulbor globe may be of any desired shape. In the form shown, the bulb a.,which surrounds the carbons, is closed at its lower end, and its open,upper end is closed when in use by a cap or plate b, having an annulargroove 10* on its under face within which the upper edge of the bulbfits. A supporting bow c carries a ring 11 at its lower end which fitsover a tip 12 on the lower end of the bulb. The upper ends of the bowextend through openings in the cap or plate b and have thumb nuts 13threaded thereon, which engage the upper face of the plate and securethe bow and bulb in position. Other arrangements of the arc-inclosingbulb may be employed without departure from the essentials of theinvention.

Cap b is provided with an opening through which the shiftable positiveelectrode d extends, and, in order that the joint may be as tight aspossible, a thimble 14 is provided. This thimble, preferably formed ofbrass, is threaded into an opening in the cap plate with its shoulderedportion 15 in engagement with the upper face thereof, and is providedwith a central opening bored and finished to snugly fit the carbon d. Byproviding a separate thimble of soft metal, it can be readily renewedwhen there is any wear in the opening and so prevent leakage.

of air and gas around the upper carbon.

The lamp-supporting means and the devices for regulating the shift-ableupper carbon 0l may be of any suitable or desired arrangement.

The lower carbon e may be supported from the cap plate in any suitablemanner, but

preferably a U-shaped vent tube f is arranged within the bulb and isprovided at its lower end with a ring or annular support g, within whichthe lower carbon is held by a thumb screw 16.

The support g is provided with an annular channel or passage 17, formedpartly in the main body thereof and partly within a ring-shaped cappiece 18, threaded over a central boss 19 on the lower end of thesupport. Passagesy 20 lead from the annular channel 17 to the sectionsor limbs of t-he vent tube I The upper ends of the U-shaped vent tubepass through openings in the top lplate and are secured thereto andinsulated therefrom by washers 2l-and nuts 22. A nut 23 and washer 24secure one of the conductors 25l of the current supply to the tube Oneend of the vent tube 1s open to the outer air while the nut 22 forms acap to close the opposite end. Adjacent the closed end of the tube, itis provided with a hole or a series of holes 26 opening within the bulb.By .this preferred arrangement, a vent tube is provided of considerablelength, as is dey sired, which also forms a support and con` ductor forthe lower carbon, `and theyent tube is arranged within the bulb out ofthe way of the regulating clutch and other parts of the lamp. It isobvious that any suitable form of support for the carbon may be arrangedat the lower end of the U-shaped vent tube. It is also to be understoodthat the vent passage and support for the lower -carbon may be arrangedotherwise than as set forth without departure from the essentials of theinvention.

'Ihe vent passage is of considerable size so that the flow of gastherethrough will not be throttled and cause air to be drawn in throughthe opening for the shift-able electrode d. Good results have beenobtained with a vent tube having an internal diameter of 1th of an inch.The passage is of considerable length vso that air will not be tooreadily drawn in through the tube by the expansion and contraction ofthe gas therein due to the variations in temperature or puffing of t-hearc. Means are also provided fcr regulating the flow through the ventpassage -to keep the carbon consumption at the desired low minimum withcurrents of different strength. Such means is preferably arranged tovary the distance between the two ends of the passage or, in otherwords, to vary the effective volume or length of the passage, and thisobject may be effected in any desired manner. In the form lengthwise ofthe tube and are controlled by a slide valve 27 in the form of a splitsleeve surrounding the tube. By shifting the valve over the openings orholes, the distance between the points at which the Vent passage opensinto the bulb and into the outside air may be varied. It is obvious thatother arrangements of regulating openings and valves for the ventpassage could be employed. I have found that in this manner, the carbonconsumption may be varied and kept at the desired low minimum withdifferent current strengths.

In certain prior constructions, air has been admitted to thearc-inclosing globe at one point while the gas is discharged therefromat another pomt so that circulation through the globe or arc chamber ismaintained. In the present construction, howtever, the inclosing globeor arc chamber communicates withthe outer air through an elongatedpassage through which an interchange of air and combustion gas iseffected, and there is, in consequence, no circulation properly speakingthrough the arc chamber.

As heretofore indicated, the vent tube or passage is of considerablelength, and of such cross section as to permit the proper interchange oflair and gas, the proportions of the tube or passage as to lengthandcross section being determined in accordance with the amountofcurrent and the size of carbon used. With an air chamber or inclosingrent of 6 amperes, provided the length of the passage from the outlet tothe opening 26 nearest thereto is approximately 9 inches. Vith theadditional vent holes 26 placed approximately ths of an inch apartlongitudinally of the tube and beyond the lowest hole, the properadjustment of the slide valve 27 admits of the lamp being employed toproduce the favorable conditions hereinbefore set forth, with currentsof 5, 4 and 3 amperes respectively, according to the distance of theparticular hole, uncovered by the slide valve, from the outlet end ofthe passage, for example, in the form shown, when 3 amperes are used,the first or upper hole 2G is uncovered, when 4f amperes are employed,the second, and so on, and the exterior of the tube is marked with acorresponding scale.

Small sizes of carbons are more readily heated than those of larger sizeand are incandescent for greater distances from their points, so thatthey are more eicient. They have not been employed extensivelyheretofore because of their short life and excessive cost ofmaintenance. With the improved form of lamp, it has been possible toemploy carbons as small as {gt-hs of an inch in diameter, which do notrequire trimming oftener than lamps previously employed having inchcarbons, and which, with 3 amperes only, will give as much or more lightthan 5 ampere lamps employing carbons of inch diameter.

It will be noted that the vent openings 26 Ain the vent tube f arelocated at a point adjacent the arc but on the outer side of the tubeaway from the arc. By this arrangement, it is found in practice that thevent tube is not liable to clog up with carbon.

I have also found that my improvement may be advantageously employed inlamps designed to use small size carbons which are found to materiallyincrease the etliciency of thelight but which have not heretofore beenlargely used as they have necessitated frequent trimming of the lamp.But I have discovered that while the tot-al carbon consumption varieswith the amount of air present, the percentage consumption of the lowernegative or fixed carbon varies with the current density of the carbons.That is to say, as the size of the carbon decreases or as the amount ofcurrent increases, the percentage consumption of the negative or fixedcarbo-n decreases. With my improved gas or air check which is adjustablein accordance with the current used, a lamp having small sized carbonswill have the desired long life (i. e. need not be frequently trimmed)and the lamp may be employed with currents of different strength.

It is obvious that numerous changes may be made in the details ofconstruction with- .out departure from the essentials of the invention.

Having descrlbed my invention, what I claim as new and desire to secureby Letters Iatent is I l. In an electric larc lamp, a substantiallyair-tight arc-inclosing globe communicating with the outer air throughan elongated vent or diusion passage of small diameter for t-heinterchange -therethrough of air and combustion gas, the length anddiameter of said passage being definitely proportioned in accordancewith the size of carbon employed and the amount of current for which thelamp is designed to admit only the necessary amount of air, whereby thecarbon consumption is maintained at a minimum, substantially asdescribed.

2. In an elect-ric arc lamp, a substantially air-tight arc-inclosingglobe communicating with the outer air through an elongated vent ordiiusion passage of small diameter for the interchange therethrough ofair and combustion gas, the length and diameter of said passage beingdefinitely proportioned in accordance with the size of carbon employedand the amount of current for which the lamp is designed to admit onlythe necessary amount of air, whereby the carbon combustion is maintainedat a minimum and means for varying the effective length of said passagein accordance with the varying amounts of current used, substantially asdescribed.

3. In an electric arc lamp, the combination of an arc-inclosing bulb, acap closing t-he end of said bulb having an opening through which thefixed carbon slides, an elongated vent 0r diifusion tube of smalldiameter supported by said cap and extending within the bulb to form asupport for the fixed carbon, said tube communicating with the outer airand wit-h the interior of said bulb for the interchange therethrough ofair and combustion gas, the diameter of said tube and the distancebetween the inlet and outlet thereofbeing definitely proportioned inaccordance with the size of carbon employed and the amount of currentfor which the lamp is designed, to admit only the necessary amount ofair, substantially i as described.

f 4. In an electric-arc lamp, the combination with an arc-inclosingbulb, a cap-closing the end of said bulb having an'opening within whichthe movable carbon snugly lits, a vent tube arranged within the bulb andextending through said/cap and a slide valve shiftable longitudinally ofsaid tube and coperating with a/series of openings therein for varyingits ieii'ective length.

5. In an electric da/rc lamp, the combination with an arc/inclosingbulb, of a cap closing the end of said bulb having an opening throughwhich the movable carbon slides, and a U-shaped vent tube supported fromsaid ca and extending downwardly within said bu b and including at itslower portion a support for the xpd carbo'n, one of the/fifi",

limbs of said tube communicating at its end with the outer air and theother limb thereof opening into the bulb.

G. In an electric-arc lamp, the combination with v an arc-inclosingbulb, of acap closing the end of said bulb having an opening throughwhich the movable carbonV ing through which the movable carbonv slides,a Ushaped vent tube supported from said cap and extending downwardlywit-hin said bulb, said tube communicating at one end with the outer airand having a longitudinally extending series of openings adjacent itsopposite end within the bulb, a valve'sleeve mounted to slide on saidtube and coperating with said openings to vary the effective length ofthe passage through said tube. Y

8. In an electric arc lamp, the combination of an arc-inclosing bulb, acap inclosing the end of said bulb having an opening through which themovable carbon slides, and a vent or diffusion tube comprising separatelimbs supported at their upper ends by said cap and extendingdownwardlyT within said bulb and including a support for the lower fixedcarbon, said limbs communicating at their lower ends and one of thelimbs communicating at its upper end `vith the outer air, the other limbbeing closed at its upper end and having an ol'iening Within the bulband located between its ends and at its outer side, the diameter of saidtube and the effective length thereof between the inlet and outletopenings being definitely proportioned in accordance with the size ofcarbon employed and the amount of current for which the lamp isdesigned, to admit only the necessary amount of air, substantially asdescribed.

9. In an electric arc lamp, the combination with an are inclosing bulb,of a cap closing the end of said bulb, and a U-shaped vent tubesupported from said cap and extending downwardly within said bulb andincluding a support for the lowerfixed carbon, one of the limbs of saidtube communiadjacent the arc cating at its end with the outer air andthe other limb having an opening communicatingY with the arc chamberwithin the bulb, the position of which opening is located in accordancewith the size of carbon employed and `the amount of current for whichthe lamp is designed to admit only the necessary amount of air, wherebythe car bon consumption is maintained at a minimum, substantially asdescribed.

l0. In an electric arc lamp, the combina- 'tion withan arc inclosingglobe, ofa cap therefor having an opening through which the movablecarbon slides, a vent. tube comprising separate limbssupported from saidcap and extending downwardly within the bulb, one of the limbs of saidtube cominunicating at its end with the outer air and the other limbhaving an opening wit-hin the bulb, and a support at the lower portionof said tube for the fixed carbon comprising an annular member having apassage or chamber formed therein communicating with both limbs of saidvent tube, substantially as described.

1l. In an electric arc lamp, the combination with an arc inclosingglobe, of a cap therefor having an opening through which the movablecarbon slides, a U-shaped vent tube supported from said cap andextending downwardly within the bulb, said tube communicating at one endwith the outer air and having an opening at its opposite end within thebulb and a support at the lower portion of said tube for the fixedcarbon, comprising an annular member formed of separate sect-ionsthreaded together and having a passage or chamber therein cornmunicatingwith both the limbs of said U- shaped vent tube, substantially asdescribed.

l2; In an electric arc lamp, the combination with an arc-inclosing bulbof a cap closing the end of said bulb having an opening through whichthe movable carbon slides, and a U-shaped vent tube supported from saidcap and extending downwardly within said bulb and including atits lowerportion a support for the fixed carbon, one of the limbs of said tubecomn'iunicatiug at its end with the outer air and the other limb havingan openin into the bulb at a point ut on the outer side of the tube awayfrom the arc, said tube being closed to the interior of the bulb fromsaid opening to its outer end.

JOHN THULIN. Witnesses:

KATHARINE GERLACH, LILLIAN PRENTICE.

